U.S. patent application number 12/550656 was filed with the patent office on 2011-03-03 for rubber composition containing silica reinforcement and functionalized polybutadiene rubber and tires having a component thereof.
Invention is credited to William Paul Francik, Paul Harry Sandstrom, Ping Zhang, Junling Zhao.
Application Number | 20110048605 12/550656 |
Document ID | / |
Family ID | 43128318 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110048605 |
Kind Code |
A1 |
Zhang; Ping ; et
al. |
March 3, 2011 |
RUBBER COMPOSITION CONTAINING SILICA REINFORCEMENT AND
FUNCTIONALIZED POLYBUTADIENE RUBBER AND TIRES HAVING A COMPONENT
THEREOF
Abstract
This invention relates to a silica reinforcement-containing
rubber composition which contains a functionalized polybutadiene
rubber to promote a relatively low hysteretic loss to thereby
enhance its desirability for tire sidewall and subtread
applications in a sense of advantageously promoting reduced tire
rolling resistance without significantly compromising various other
desirable tire performance parameters.
Inventors: |
Zhang; Ping; (Hudson,
OH) ; Sandstrom; Paul Harry; (Cuyahoga Falls, OH)
; Francik; William Paul; (Bath, OH) ; Zhao;
Junling; (Hudson, OH) |
Family ID: |
43128318 |
Appl. No.: |
12/550656 |
Filed: |
August 31, 2009 |
Current U.S.
Class: |
152/525 |
Current CPC
Class: |
C08L 9/00 20130101; B60C
1/0016 20130101; C08J 3/203 20130101; B60C 1/0025 20130101; Y02T
10/86 20130101; C08J 2319/00 20130101; C08J 2309/00 20130101; C08L
19/006 20130101; Y02T 10/862 20130101; C08L 9/00 20130101; C08L
2666/08 20130101; C08L 19/006 20130101; C08L 2666/08 20130101 |
Class at
Publication: |
152/525 |
International
Class: |
B60C 1/00 20060101
B60C001/00 |
Claims
1. A pneumatic tire having at least one of an outer sidewall rubber
layer and subtread rubber layer of a rubber composition comprised
of, based on parts by weight per 100 parts by weight of rubber
(phr): (A) Conjugated diene-based elastomers comprised of: (1)
about 20 to about 80 phr of: (a) a siloxy functionalized cis
1,4-polybutadiene elastomer having an end terminating group
reactive with hydroxyl groups contained on said precipitated silica
provided by a terminating compound represented by the general
formula (I): X.sub.nSi(OR).sub.mR'.sub.4-m-n (I) where X can be a
halogen atom selected from a chlorine atom, a bromine atom and an
iodine atom; R can be an alkyl group with from about 1 to about 7
carbon atoms; R' is a alkyl group with from about 1 to about 20
carbon atoms, an aryl group, a vinyl group or a halogenated alkyl
group; m is an integer of 1, 2, 3, or 4, n is an integer of 0, 1,
or about 2, and the sum of n and m is 1, 2, 3, or4. (b) an amine
functionalized cis 1,4-polybutadiene elastomer having an end
terminating amine group reactive with hydroxyl groups contained on
said precipitated silica (c) a siloxy-aldimine functionalized cis
1,4-polybutadiene elastomer having an end terminating group
reactive with hydroxyl groups contained on said precipitated silica
provided by a terminating compound containing a siloxy and an
aldimine group represented by the general formula (II):
RCH.dbd.N(CH.sub.2).sub.xSi(OR.sup.1).sub.yR.sup.2.sub.3-y wherein
R represents a group consisting of an aryl or substituted aryl
having 6 to 18 carbon atoms, or a heterocycle or heteroaryl having
3 to 18 carbon atoms; R.sup.1 and R.sup.2 may be the same or
different and each independently represents a group having 1 to 18
carbon atoms selected from an alkyl, a cycloalkyl, an allyl, or an
aryl; X is an integer from 1 to 20; and Y is an integer from 1 to
3. (2) about 20 to about 80 phr of at least one additional
conjugated diene based elastomer (in addition to said
functionalized cis 1,4-polybutadiene elastomers) comprised of at
least one of polymers of at least one of isoprene and 1,3-butadiene
and copolymers of styrene and at least one of isoprene and
1,3-butadiene, and (B) about 30 to about 70 phr of rubber
reinforcing filler comprised of rubber reinforcing carbon black and
synthetic amorphous silica (precipitated silica) as: (1) about 20
to about 60 phr of said rubber reinforcing carbon black, and (2)
about 20 to about 60 phr of said precipitated silica, and (C)
coupling agent for said precipitated silica having a moiety
reactive with hydroxyl groups on said precipitated silica (e.g.
silanol groups) and another different moiety interactive with said
elastomer(s).
2. The tire of claim 1 where said component is an outer tire
sidewall rubber layer.
3. The tire of claim 1 wherein said component is a tire subtread
rubber layer.
4. The tire of claim 1 wherein said outer tire sidewall rubber
layer subtread rubber layer is exclusive of cord reinforcement.
5. The tire of claim 1 wherein said subtread rubber layer is
exclusive of cord reinforcement.
6. The tire of claim 1 wherein said functionalized cis
1,4-polybutadiene elastomer is a siloxy functionalized cis
1,4-polybutadiene elastomer elastomer having an end terminating
group reactive with hydroxyl groups contained on said precipitated
silica provided by a terminating compound represented by said
general formula (I).
7. The tire of claim 1 wherein said functionalized cis
1,4-polybutadiene elastomer 5 is a tetraethyl orthosilicate
terminated 1,4-polybutadiene elastomer.
8. The tire of claim 1 wherein said functionalized cis
1,4-polybutadiene elastomer is an amine functionalized cis
1,4-polybutadiene elastomer having an end terminating amine group
reactive with hydroxyl groups contained on said precipitated
silica.
9. The tire of claim 1 wherein said functionalized cis
1,4-polybutadiene elastomer is a siloxy-aldimine functionalized cis
1,4-polybutadiene elastomer having an end terminating group
reactive with hydroxyl groups contained on said precipitated silica
provided by a terminating compound represented by said general
formula (II).
10. The tire of claim 1 wherein said functionalized cis
1,4-polybutadiene elastomer is a siloxy functionalized cis
1,4-polybutadiene elastomer having an end terminating group
reactive with hydroxyl groups contained on said precipitated silica
provided by a terminating compound as a tetraethyl orthosilicate
represented by said general formula (III)
11. The tire of claim 1 wherein said functionalized cis
1,4-polybutadiene elastomer is a siloxy-aldimine functionalized cis
1,4-polybutadiene elastomer having an end terminating group
reactive with hydroxyl groups contained on said precipitated silica
provided by a terminating compound represented by said general
formula (IV).
12. The tire of claim 11 wherein said terminating compound is
comprised of N-benzylidene-3-(triethoxysilyl)-1-propaneamine or
N-naphthylidene-3-(triethoxysilyl)-1-propaneamine.
13. The tire of claim 11 wherein said wherein said end terminating
compound containing a siloxy and an aldimine group is represented
by the general formula (IV):
RCH.dbd.N(CH.sub.2).sub.xSi(OCH.sub.2)CH.sub.3 (IV) where R is an
aryl or substituted aryl group having from 6 to 18 carbon atoms, or
a heterocycle or heteroaryl group having from 3 to 18 carbon atoms,
and where x is an integer in a range of from 1 to 20.
14. The tire of claim 1 wherein said rubber composition for said
outer sidewall rubber layer is prepared by mixing steps comprised
of: (A) mixing rubber reinforcing carbon black, precipitated silica
and silica coupling agent together with said elastomer(s) in a
preparatory non-productive mixing step, followed by a productive
mixing step in which sulfur curatives are added, or (B) mixing
precipitated silica, together with coupling agent, together with
said elastomer(s) in a first preparatory non-productive mixing step
followed by mixing rubber reinforcing carbon black in a subsequent
second non-productive mixing step to the rubber composition from
said first non-productive mixing step, followed by a productive
mixing step in which sulfur curatives are added, or (C) mixing
carbon black with said elastomer(s) in a preparatory first
non-productive mixing step followed by mixing precipitated silica
and coupling agent in a subsequent non-productive mixing step with
the rubber composition from said first non-productive mixing step,
followed by a productive mixing step in which sulfur curatives are
added.
15. The tire of claim 14 wherein said rubber composition for said
outer sidewall rubber layer is prepared by mixing steps comprised
of mixing rubber reinforcing carbon black, precipitated silica and
silica coupling agent together with said elastomer(s) in a
preparatory non-productive mixing step, followed by a productive
mixing step in which sulfur curatives are added, wherein said
mixing steps are conducted in an internal rubber mixer to a
temperature in a range of from about 140.degree. C. to about
170.degree. C. for said non-productive steps and to a temperature
in a range of from about 100.degree. C. to about 120.degree. C. for
said productive mixing steps, and wherein said rubber compositions
are cooled to a temperature below 40.degree. C. between said mixing
steps.
16. The tire of claim 14 wherein said rubber composition for said
outer sidewall layer is prepared by mixing precipitated silica,
together with coupling agent, together with said elastomer(s) in a
first preparatory non-productive mixing step followed by mixing
rubber reinforcing carbon black in a subsequent second
non-productive mixing step with the rubber composition from said
first non-productive mixing step, followed by a productive mixing
step in which sulfur curatives are added, wherein said mixing steps
are conducted in an internal rubber mixer to a temperature in a
range of from about 140.degree. C. to about 170.degree. C. for said
non-productive steps and to a temperature in a range of from about
100.degree. C. to about 120.degree. C. for said productive mixing
steps, and wherein said rubber compositions are cooled to a
temperature below 40.degree. C. between said mixing steps.
17. The tire of claim 14 wherein said rubber composition for said
rubber outer sidewall layer is prepared by mixing carbon black with
said elastomer(s) in a preparatory first non-productive mixing step
followed by mixing precipitated silica and coupling agent in a
subsequent non-productive mixing step with the rubber composition
from said first non-productive mixing step, followed by a
productive mixing step in which sulfur curatives are added; wherein
said mixing steps are conducted in an internal rubber mixer to a
temperature in a range of from about 140.degree. C. to about
170.degree. C. for said non-productive steps and to a temperature
in a range of from about 100.degree. 0 C. to about 120.degree. C.
for said productive mixing steps, and wherein said rubber
compositions are cooled to a temperature below 40.degree. C.
between said mixing steps.
Description
FIELD OF INVENTION
[0001] This invention relates to a silica reinforcement-containing
rubber composition which contains a functionalized polybutadiene
rubber to promote a relatively low hysteretic loss to thereby
enhance its desirability for tire sidewall and subtread
applications in a sense of advantageously promoting reduced tire
rolling resistance without significantly compromising various other
desirable tire performance parameters.
BACKGROUND OF THE INVENTION
[0002] It is sometimes desired to provide vehicular rubber tires
with reduced rolling resistance to promote fuel economy for the
associated vehicle.
[0003] The use of silica reinforcement together with a silica
coupling agent in a tread rubber composition has been mentioned for
promoting improved (reduced) rolling resistance for a tire where a
solution polymerization prepared styrene/butadiene rubber (S-SBR)
is used (for example see U.S. Pat. No. 5,227,425) and where a
functionalized styrene/butadiene rubber is used (for example see
U.S. Pat. Nos. 7,202,306 and 7,222,650).
[0004] Rubber compositions with reduced reinforcing filler contents
(for example reduced carbon black contents), rubber compositions
with increased crosslinking density and rubber compositions which
contain one or more elastomers with a relatively low glass
transition temperature (Tg) have been proposed for tire treads to
promote a reduction in the rubber hysteresis of the tread and an
associated lower rolling resistance for the tire itself.
[0005] However, it is well known to those skilled in such art that
reducing the tire tread rubber hysteresis for a purpose of reducing
the rolling resistance of the tire typically results in a reduction
of one or more other desirable tire tread properties such as, for
example, a reduction in tread traction, or tread grip.
[0006] It is therefore desirable to promote a reduction in
hysteresis of a rubber composition for a tire component, usually
predictive of an increased rebound property of the rubber
composition itself, to thereby promote a reduction in a tire's
rolling resistance without significantly degrading one or more
various other tire performance properties.
[0007] Such contemplated tire components for this invention are a
tire sidewall, particularly an outer tire sidewall rubber layer
which does not contain cord reinforcement and is exposed to
atmosphere conditions, physical scuffing and substantial flexing,
as well as a tire undertread (which might be referred to as a
subtread) rubber layer which also does not contain cord
reinforcement and which underlies the tire outer tread rubber layer
with its running surface for the tire tread. Such undertread rubber
layer may be found in a tire with a tread of a cap/undertread
construction with an outer tread cap rubber layer which contains
the running surface of the tire and an undertread rubber layer as a
tread base layer or an intermediate rubber layer positioned
intermediately between a tread outer rubber cap layer and a tread
base rubber layer.
[0008] A significant aspect of this invention is a focus on a
tire's undertread (subtread) rubber layer in a sense that the
rubber composition used for the undertread rubber layer may be used
to promote a reduced rolling resistance for the tire in the sense
of the rubber composition having a higher rebound value, without
significantly compromising various other physical properties of the
tread, and to thereby promote an increased fuel efficiency for an
associated vehicle.
[0009] An additional significant aspect of this invention is a
focus upon an outer tire sidewall rubber layer which also
contributes to a tire's rolling resistance because of its
relatively large deformation (e.g. considerable flexing) during
working of the tire where hysteresis loss of its rubber composition
and associated tendency of increased internal heat generation may
be a factor as described in a paper entitled "Fundamentals of
Rolling Resistance" published in Rubber Chemistry and Technology,
Volume 74(3), Pages 525 through 539 (year 2001). This is considered
significant for use of the rubber composition as an outer tire
sidewall rubber layer in a sense of the rubber composition
demonstrating a higher rebound value and therefore promoting a
prospectively lower internal heat generation and lower hysteresis
loss and thereby promoting an increased fuel efficiency for an
associated vehicle.
[0010] A unique advantage of promoting a reduction in rolling
resistance of tires through the modification of the rubber
composition of the outer tire sidewall component, whether by
material variations or by structural changes to promote a reduced
hysteresis loss of the sidewall rubber composition is that tire
tread tire performances, such as treadwear and traction, are less
likely to be compromised.
[0011] In practice, an outer tire sidewall component is often
comprised of a mixture of natural rubber and polybutadiene rubber.
Particulate rubber reinforcement in a form of carbon black is
historically used in the rubber composition for the outer sidewall
rubber layer.
[0012] In some instances, an inclusion of silica together with
carbon black has been suggested for tire sidewall rubber
compositions. For example, see U.S. Pat. No. 5,244,028 in which a
small quantity of silica in an amount of about 1.0 to 5.0 phr, with
low pH values to promote resistance to weathering, and U.S. Pat.
No. 6,046,266 with about 20 to 60 phr of silica, together with
natural rubber and polybutadiene rubber, to promote an increase in
durability and cut growth resistance for the rubber
composition.
[0013] It has now been discovered that hysteresis loss of a rubber
composition can be significantly reduced through the use of a
functionalized polybutadiene rubber in combination with silica and
a silica coupling agent which may be suitable for use as a tire
component such as for a tire subtread or tire outer sidewall
component, to promote reduced rolling resistance of the tire
without significantly degrading one or more other performance
factors for the tire.
[0014] The term "subtread" relates to a portion of a vehicular tire
tread of a multilayered configuration with an outer circumferential
tread cap rubber layer with a running surface for ground-contacting
purposes and an underlying rubber tread layer which underlies the
tread cap rubber layer and is referred to herein as a "subtread" or
"undertread". It is usually not intended to be ground-contacting.
For some tread configurations, the subtread is considered as being
a tread base rubber layer which interfaces with an underlying
overlay layer or tread belt layer. In other tread configurations,
the subtread may be an intermediate tread rubber layer positioned
between the outer tread cap rubber layer and a tread base rubber
layer.
[0015] The term "sidewall" component refers to an outer tire
sidewall rubber layer normally positioned outside of (axially
outward from) the tire carcass ply layers and usually an outer
sidewall rubber layer which may be visually observable and
atmospherically exposed. Such sidewall rubber layer is usually
subject to extensive flexing scuffing as would be well known to one
having skill in such art.
[0016] In the description of this invention, the term "phr" where
used relates to parts by weight of an ingredient per 100 parts by
weight of rubber, unless otherwise indicated.
[0017] The terms "rubber" and "elastomer" are used interchangeably
unless otherwise indicated. The terms "vulcanized" and "cured" are
used interchangeably unless otherwise indicated. The terms
"compound" and "rubber composition" may be used interchangeably
unless indicated.
SUMMARY AND PRACTICE OF THE INVENTION
[0018] In accordance with this invention a pneumatic tire is
provided having at least one of an outer sidewall rubber layer and
subtread component of a rubber composition comprised of, based on
parts by weight per 100 parts by weight of rubber (phr):
[0019] (A) Conjugated diene-based elastomers comprised of: [0020]
(1) about 20 to about 80 phr of: [0021] (a) a siloxy functionalized
cis 1,4-polybutadiene elastomer having an end terminating group
reactive with hydroxyl groups contained on said precipitated silica
provided by a terminating compound represented by the general
formula (I):
[0021] X.sub.nSi(OR).sub.mR'.sub.4-m-n (I) [0022] where X can be a
halogen atom selected from a chlorine atom, a bromine atom and an
iodine atom; R can be an alkyl group with from about 1 to about 7
carbon atoms (e.g., 1, 2, 3, 4, 5, 6, or 7 carbon atoms); R' is a
alkyl group with from about 1 to about 20 carbon atoms, an aryl
group, a vinyl group or a halogenated alkyl group; m is an integer
of 1, 2, 3, or 4, n is an integer of 0, 1, or about 2, and the sum
of n and mis 1, 2, 3, or 4. [0023] (b) an amine functionalized cis
1,4-polybutadiene elastomer having an end terminating amine group
reactive with hydroxyl groups contained on said precipitated silica
[0024] (c) a siloxy-aldimine functionalized cis 1,4-polybutadiene
elastomer having an end terminating group reactive with hydroxyl
groups contained on said precipitated silica provided by a
terminating compound containing a siloxy and an aldimine group
represented by the general formula (II):
[0024] RCH.dbd.N(CH.sub.2).sub.xSi(OR.sup.1).sub.yR.sup.2.sub.3-y
[0025] wherein R represents a group consisting of an aryl or
substituted aryl having 6 to 18 carbon atoms, or a heterocycle or
heteroaryl having 3 to 18 carbon atoms; R.sup.1 and R.sup.2 may be
the same or different and each independently represents a group
having 1 to 18 carbon atoms selected from an alkyl, a cycloalkyl,
an allyl, or an aryl; X is an integer from 1 to 20; and Y is an
integer from 1 to 3. [0026] (2) about 20 to about 80 phr of at
least one additional conjugated diene based elastomer (in addition
to said functionalized cis 1,4-polybutadiene elastomers) comprised
of at least one of polymers of at least one of isoprene and
1,3-butadiene and copolymers of styrene and at least one of
isoprene and 1,3-butadiene, and
[0027] (B) about 30 to about 70 phr of rubber reinforcing filler
comprised of rubber reinforcing carbon black and synthetic
amorphous silica (precipitated silica) as: [0028] (1) about 20 to
about 60 phr of said rubber reinforcing carbon black, and [0029]
(2) about 20 to about 60 phr of said precipitated silica, and
[0030] (C) coupling agent for said precipitated silica having a
moiety reactive with hydroxyl groups on said precipitated silica
(e.g. silanol groups) and another different moiety interactive with
said elastomer(s).
[0031] For the above mentioned siloxy functionalized cis
1,4-polybutadiene elastomer of the above Formula I, in some
embodiments, it is considered that one or more of the --OR group(s)
are hydrolyzable, by, for example, steam stripping procedures (such
as those disclosed in U.S. Pat. No. 5,066,721).
[0032] For the siloxy terminated cis 1,4-polybutadiene elastomer of
the above Formula I, an example of a terminating compound is TEOS,
or tetraethyl orthosilicate, where the associated cis
1,4-polybutadiene elastomer might be referred to as a TEOS
terminated 1,4-polybutadiene elastomer, and where the TEOS may be
represented by the general formula (III):
Si(OCH.sub.2CH.sub.3).sub.4 (III)
[0033] In general the terminating compound to prepare the siloxy
terminated cis 1,4-polybutadiene elastomer can be synthesized, or
prepared, by various methods, including, for example, methods
presented in U.S. Pat. No. 5,066,721, which is herein incorporated
by reference in its entirety.
[0034] For the above mentioned siloxy-aldimine terminated cis
1,4-polybutadiene elastomer of the above Formula II, in one
embodiment, for the terminating compound for preparation of the
functionalized cis 1,4-polybutadiene elastomer R is selected from
phenyl, substituted-phenyl, naphthyl, substituted-naphthyl, or
heteroaryl groups. In another embodiment, R is phenyl. In a further
embodiment, at least one R.sup.1 group is an ethyl radical.
[0035] In practice, for the siloxy-aldimine terminated cis
1,4-polybutadiene elastomer of the above Formula II, it is
envisioned that the aldimino group can hydrogen bond with a variety
of acidic functional groups and is susceptible to nucleophilic
addition at the imine carbon. It is envisioned that the siloxy
group can undergo a condensation reaction with a silanol group on
the surface of silica and is susceptible to nucleophilic
substitution at the silicon atom.
[0036] In a further embodiment of the siloxy-aldimine cis
1,4-polybutadiene elastomer of the above Formula II, the
terminating compound bearing the siloxy and aldimine groups may be
represented by the general formula (IV):
RCH.dbd.N(CH.sub.2).sub.xSi(OCH.sub.2)CH.sub.3, (IV)
(which may sometimes be referred herein to as an "imine-TEOS"
compound, with TEOS being an abbreviation for tetraethyl
orthosilicate, and the resulting functionalized cis
1,4-polybutadiene elastomer may be referred to as an "imine-TEOS
functionalized cis 1,4-polybutadiene elastomer"),
[0037] where R is an aryl or substituted aryl group having from 6
to 18 carbon atoms, or a heterocycle or heteroaryl group having
from 3 to 18 carbon atoms, and where x is an integer in a range of
from 1 to 20.
[0038] A significant aspect of the invention is a tire having a
sidewall component of said rubber composition which contains said
functionalized cis 1,4-polybutadiene elastomer in a sense that it
has been observed that the presence of the functionalized elastomer
in the rubber composition which contains both carbon black and
silica reinforcement contributed to enhancing its rebound physical
property which is indicative of promoting a reduction in rolling
resistance and reduction in internal heat generation, reduction in
hysteresis, of the tire having such sidewall component and hence a
predictive fuel economy, or savings, for an associated vehicle.
[0039] A further significant aspect of the invention is a tire
having a circumferential subtread layer of a rubber composition
which contains said functionalized cis 1,4-polybutadiene elastomer
in a sense that it has been observed that the presence of the
functionalized elastomer in the rubber composition which contains
both carbon black and silica reinforcement contributed to enhancing
its rebound physical property which is indicative of promoting a
reduction in rolling resistance of the tire having a tread of such
subtread component and hence a fuel economy, or savings, for an
associated vehicle.
[0040] For the amine functionalized cis 1,4-polybutadine elastomer,
a representative example is BR 1256H.TM. from the Nippon Zeon
Company.
[0041] For the alkoxy terminated cis 1,4-polybutadiene of Formula
I, a TEOS functionalized cis 1,4-polybutadiene may be prepared, for
example, by polymerizing 1,3-butadiene monomer to form a polymer by
using an organolithium compound as an initiator in a hydrocarbon
solvent and reacting an active terminal end of the polymer with a
functionalized terminating agent represented by the General Formula
I.
[0042] For the alkoxy-imine functionalized cis 1,4-polybutadiene
elastomer of Formula II, an imine-TEOS functionalized cis
1,4-polybutadiene may be prepared, for example, by polymerizing
monomers comprised of 1,3-butadiene and at least one amine monomer
and to form a polymer with amine functionality in its molecular
chain followed by reacting an active terminal end of the polymer
with a functionalized terminating compound to provide a terminating
group on the polymer, wherein the terminating compound is comprised
of the general Formula (IV), which is considered herein as being a
variation of Forumla (II).
[0043] Representative of such amine monomer is, for example:
##STR00001##
[0044] A representative example of such functionalized terminating
agent taken from Formula (IV) is, for example,
N-benzylidene-3-(triethoxysilyl)-1-propaneamine or
N-naphthylidene-3-(triethoxysilyl)-1-propaneamine.
[0045] In practice, representative of various of said additional
diene-based elastomers for the rubber compositions are comprised
of, for example, polyisoprene rubber (both natural polyisoprene
rubber such as for example SMR20, namely smoked rubber sheet number
20, and synthetic polyisoprene rubber such as, for example,
NAT2200.TM. from The Goodyear Tire & Rubber Company) and cis
1,4-polybutadiene as CB25.TM. from the Lanxess Company,
styrene/butadiene rubber and non-functionalized cis
1,4-polybutadiene rubber.
[0046] It is readily understood by those having skill in the art
that the rubber composition can be prepared, or compounded, by
methods generally known in the rubber compounding art, such as, for
example, mixing the various sulfur-vulcanizable constituent rubbers
with various commonly used additive materials such as, for example,
curing aids, such as sulfur, activators, retarders and
accelerators, processing additives, such as oils, resins including
tackifying resins and plasticizers, pigments, fatty acid, zinc
oxide, waxes, antioxidants and antiozonants and peptizing agents.
As known to those skilled in the art, depending on the intended use
of the sulfur vulcanizable and sulfur vulcanized material
(rubbers), the additives mentioned above are selected and commonly
used in conventional amounts.
[0047] The presence and relative amounts of the above additives are
not considered to be an aspect of the present invention, unless
otherwise indicated herein.
[0048] The tires can be built, shaped, molded and cured by various
methods which will be readily apparent to those having skill in
such art.
[0049] The following examples are provided to further illustrate
the invention where amounts and percentages of materials are
presented in terms of weight unless otherwise indicated.
EXAMPLE I
[0050] Rubber compositions (rubber compounds) composed of a
combination of natural rubber (cis 1,4-polyisoprene rubber) and
various cis 1,4-polybutadiene elastomers, including functionalized
cis 1,4-polybutadiene elastomers, were prepared.
[0051] Rubber compound 1 was a Control rubber composition which
used a combination of natural rubber and cis 1,4-polybutadiene
rubber A.
[0052] Rubber compound 2 was also a Control rubber composition
which used a combination of natural rubber and cis
1,4-polybutadiene rubber B, where the cis 1,4-polybutadiene rubber
was prepared by polymerizing 1,3-butadiene monomer in the presence
of a neodymium containing catalyst system such as, for example,
CB25.TM. from the Lanxess Company.
[0053] Rubber compound 3 was a rubber composition which used a
combination of natural rubber and an amine functionalized cis
1,4-polybutadiene rubber C as BR 1256H.TM. from the Nippon Zeon
Company.
[0054] Rubber compound 4 was a rubber composition which contained a
combination of natural rubber and a TEOS functionalized cis
1,4-polybutadiene rubber D, referred to herein as BR TEOS, from The
Goodyear Tire & Rubber Company.
[0055] Rubber compound 5 was a rubber composition which contained a
combination of natural rubber and a TEOS-imine functionalized cis
1,4-polybutadiene rubber E, referred to herein as BR Imine-TEOS,
from The Goodyear Tire & Rubber Company.
[0056] The rubber compositions were prepared by mixing the
ingredients in three sequential mixing steps, namely two
non-productive (NP1 and NP2) followed by a productive mixing step
(PR) in an internal rubber mixer. The dump temperature from the
internal rubber mixer after completing the NP1 and NP2 mixing steps
was 160.degree. C. The dump temperature after completing the
subsequent PR mixing step was 110.degree. C.
[0057] For this Example, both of the carbon black and silica
reinforcement fillers as well as the silica coupling agent were
added in the NP1 non-productive mixing stage with the respective
cis 1,4-polybutadiene elastomers.
[0058] The basic recipe for the rubber compounds is presented in
the following Table 1 and recited in parts by weight unless
otherwise indicated.
TABLE-US-00001 TABLE 1 Parts First Non-Productive Mixing Step
(NP1), mixed to about 160.degree. C. Cis 1,4-Polyisoprene natural
rubber.sup.1 50 Polybutadiene elastomers A and B and functionalized
50 polybutadienes C, D and E.sup.2 Carbon black N550 30
Silica.sup.3 30 Silica coupling agent.sup.4 2.4 Rubber processing
oil and resin 7 Wax and antioxidant 5.5 Stearic acid 1 Second
Non-Productive Mixing Step (NP2), mixed to about 160.degree. C. No
ingredients added in this mixing step, sometimes referred to as
"re-milling" Non-Productive Mixing Step (PR), (mixed to about
110.degree. C.) Sulfur 1.5 Zinc oxide 1.5 Antioxidant 1.25
Sulfenamide sulfur cure accelerator 2.1 .sup.1Natural rubber as
SMR20 having a cis 1,4 content of about 99.8 percent and a Tg of
about -65.degree. C. .sup.2A Cis 1,4-polybutadiene rubber A as BUD
1208 .TM. from the Goodyear Tire & Rubber company having a cis
1,4 content of at least about 97 percent and a Tg of about
-106.degree. C. .sup.2B Cis 1,4-polybutadiene B prepared by
polymerizing 1,3-butadiene monomer by Neodymium catalysis as CB25
.TM. from the Lanxess Company reportedly having a cis 1,4 content
of at least about 98 percent and a Tg of about -106.degree. C.
.sup.2C Amine-functionalized cis 1,4-polybutadiene rubber C, as BR
1256H .TM. from the Nippon Zeon Company reportedly having a Tg of
about -94.degree. C. .sup.2D TEOS-functionalized cis
1,4-polybutadiene rubber D, from The Goodyear Tire & Rubber
Company having a Tg of about -93.degree. C. .sup.2E
Imine-TEOS-functionalized cis 1,4-polybutadiene rubber E, from The
Goodyear Tire & Rubber Company having a Tg of about -95.degree.
C. .sup.3Precipitated silica as Hi-Sil 243 from the PPG company
having an indicated BET surface area of 135 m.sup.2/g .sup.4Silica
coupling agent comprised of bis(3-triethoxysilylpropane)
polysulfide having an average in a range of from about 2 to about
2.6 connecting sulfur atoms in its polysulfidic bridge as Si266
.TM. from the Evonik/Degussa Company
[0059] The following Table 2 illustrates processing characteristics
and various physical properties of rubber compositions based upon
the basic recipe of Table 1.
TABLE-US-00002 TABLE 2 Rubber Compound Numbers 1 2 3 4 5 Elastomers
(phr) Natural Rubber 50 50 50 50 50 Cis 1,4-polybutadiene A 50 0 0
0 0 Cis 1,4-polybutadiene B 0 50 0 0 0 Amine functionalized
polybutadiene C 0 0 50 0 0 TEOS functionalized polybutadiene D 0 0
0 50 0 Imine-TEOS functionalized 0 0 0 0 50 polybutadiene E
Rheometer (RPA Analyzer).sup.1, 170.degree. C. Maximum torque (dNm)
14.7 15.5 17.1 17.9 17.8 Minimum torque (dNm) 2.5 2.9 2.8 3.7 4.6
T90 (minutes) 3.6 3.6 3.9 3.9 3.9 Mooney Scorch, 120.degree. C.
Scorch time 5 pt rise (minutes) 36.7 34.7 33.8 32.4 36 RPA
Analyzer.sup.1, 100.degree. C. Cured G' at 1% strain (MPa) 2.2 2
2.3 2.4 2.1 Cured G' at 10% strain (MPa) 1.3 1.3 1.5 1.6 1.5 Tan
delta at 10% strain 0.164 0.142 0.138 0.131 0.119 Stress-strain,
ATS.sup.2, 11 min, 170.degree. C..sup.2 Tensile strength (MPa) 18.1
19.2 19.2 18.1 18.5 Elongation at break (%) 707 688 647 642 601
100% modulus (MPa) 1.3 1.3 1.5 1.5 1.6 300% modulus (MPa) 6.2 6.5
6.6 6.5 7.5 Rebound 23.degree. C. 48.9 53.6 56.9 57.4 59.1
100.degree. C. 58.5 62.3 65.2 66.4 68.3 Shore A Hardness 23.degree.
C. 59 59 61 61 61 100.degree. C. 54 54 56 57 57 DIN Abrasion.sup.3,
23.degree. C. Relative Vol. Loss 80 70 76 75 72 RDS.sup.4 Strain
Sweep, 10 Hertz, 30.degree. C. Storage modulus (G'), at 10% 1.5 1.6
1.7 1.8 1.8 strain, (MPa) Tan delta, at 10% strain 0.162 0.139
0.126 0.118 0.118 .sup.1Data according to Rubber Process Analyzer
as RPA 2000 .TM. .sup.2Data according to Automated Testing System
(ATS) instrument by the Instron Corporation which incorporates six
tests in one system. Such instrument may determine ultimate
tensile, ultimate elongation, moduli, etc. Modulus data reported in
the Table is generated by running the ring tensile test.
.sup.3DIN-53516 .sup.4Data by rheometric spectrometric analytical
instrument
[0060] It can be seen from Table 2 that the replacement of the cis
1,4 polybutadiene rubber A in rubber compound 1 with cis
1,4-polybutadiene rubber B in rubber compound 2 or functionalized
polybutadiene rubber Samples C through E in rubber compounds 3, 4
and 5, respectively, did not significantly affect the rubber
composition processing, such as the Mooney scorch time, and cure
dynamics, measured by MDR which included the T90 cure time, of the
rubber composition.
[0061] This is considered to be significant, as will be further
discussed hereafter, in a sense that observed enhancement of
physical properties of the rubber composition such as rebound and
tan delta, which is indicative of beneficial hysteresis reduction,
or loss by the use of functionalized polybutadienes C through E of
rubber compounds 3, 4 and 5 instead of the non-functionalized
polybutadiene elastomers A and B of rubber compounds 1 and 2, all
of which included precipitated silica reinforcement together with a
silica coupling agent, was not obtained at the expense of
processibility of the rubber composition, insofar as the Mooney
scorch time, as well as T90 cure time were concerned.
[0062] It can be seen from Table 2 that the rebound values at room
temperature (about 23.degree. C.) and rebound values at high
temperature (100.degree. C.) of the rubber composition were
significantly improved (increased) as a result of replacing the cis
1,4-polybutadiene A with the amine, TEOS and imine-TEOS
functionalized polybutadiene elastomers C through E. Also, the
hysteresis loss indicative tan delta property at 30.degree. C. of
the rubber composition was significantly enhanced (reduced) as a
result of replacing the non-functionalized cis 1,4-polybutadiene
elastomer A and B with the amine, TEOS and imine-TEOS
functionalized cis 1,4-polybutadiene elastomers C through E.
[0063] For example, it is seen that the rebound values at
23.degree. C. and 100.degree. C. of the experimental Rubber
compound 5, using imine-TEOS functionalized polybutadiene elastomer
E were beneficially about 10 points higher than that of the
comparative (Control) rubber compound 1 using the
non-functionalized polybutadiene elastomer A.
[0064] Also, it can further be seen that the hysteresis loss
indicative tan delta at 30.degree. C. of the rubber composition was
significantly enhanced (reduced) as a result of replacing the
non-functionalized cis 1,4-polybutadiene elastomer A or B of rubber
compounds 1 and 2 with the amine, TEOS and imine-TEOS
functionalized cis 1,4-polybutadiene elastomers C through E of the
rubber compounds 3, 4 and 5, respectively.
[0065] In particular, the tan delta value for rubber compounds 3, 4
and 5 using the functionalized cis 1,4-polybutadiene elastomers
were only 0.126, 0.118 and 0.118, respectively, and therefore
significantly lower than the value of 0.162 for comparative
(Control) rubber compound 1.
[0066] It can also be seen that indication of hysteresis loss as
suggested by the indicated tan delta values at 100.degree. C. of
the rubber compound 5 using imine-TEOS functionalized polybutadiene
E, for example, was significantly lower than that of the
comparative (Control) rubber compound 1 using the
non-functionalized cis 1,4-polybutadiene A.
[0067] It is noted that some improvement in rebound value and
hysteresis loss tan delta value was observed for comparative
(Control) rubber compound 2 as compared to comparative (Control)
rubber compound 1 in which non-functionalized polybutadiene A was
replaced by the non-functionalized polybutadiene B. However, the
extent of improvement was not as significant as the extent of
improvement observed for rubber compounds 3, 4 and 5 using
functionalized polybutadienes C through E. Overall, it is seen that
the greatest improvement was observed for rubber compounds 4 and 5
which used TEOS functionalized polybutadiene D and imine-TEOS
functionalized polybutadiene E, respectively, which were observed
to be the most effective in enhancing the hysteresis loss
properties of the rubber composition.
[0068] This is considered to be significant in the sense that the
rubber compounds 3, 4 and 5 with their observed beneficial high
rebound values and low hysteresis loss tan delta values at room
temperature (about 23.degree. C.) and at high temperature
(100.degree. C.) are considered herein to be predictive of a
relatively low rate of internal heat built up, with an attendant
relatively low rate of internal temperature rise to promote a
resultant beneficially reduced rolling resistance for a vehicular
tire having an outer tire sidewall rubber layer or subtread rubber
layer (component) composed of such rubber composition with a
resultant expected improved fuel economy for an associated vehicle
using such tire as compared to using the non-functionalized
polybutadiene elastomers in the rubber compound.
[0069] It can also further be seen from Table 2 that the abrasion
resistance of the rubber composition was in general improved or at
least maintained for silica reinforcement-containing rubber
compounds 3, 4 and 5, using the functionalized polybutadiene
rubbers C through E, as compared to comparative (Control) rubber
compound 1 using the non-functionalized polybutadiene rubber.
[0070] This is considered to be significant in a sense that the
enhancement of compound hysteresis properties from the use of
functionalized polybutadienes C through E for rubber compounds 3, 4
and 5 in combination with the precipitated silica and silica
coupling agent was not obtained at the expense of abrasion
resistance of the rubber composition.
[0071] This example demonstrates the desirability and benefit of
using a functionalized polybutadiene such as functionalized
polybutadienes C through E, which contained precipitated silica
reinforcement, for enhanced rubber composition hysteresis loss
properties, for an outer tire sidewall rubber layer or subtread
rubber layer (component) for a vehicular tire composed of such
rubber composition with a resultant expected improved, hence a
predictive improved, rolling resistance performance for the tire
without significantly compromising the abrasion resistance
property.
EXAMPLE II
[0072] Rubber compositions (rubber compounds) composed of a
combinations of natural rubber (cis 1,4-polyisoprene rubber) and
various polybutadiene rubbers, as well as rubber compositions
containing functionalized cis 1,4-polybutadiene elastomers, were
prepared.
[0073] The rubber compounds 1 through 5 for of Example I are
similar to rubber compounds 6 through 10, respectively, for this
Example II insofar as the polybutadiene and functionalized
polybutadiene elastomers used.
[0074] For this Example II, the rubber compositions (compounds)
were prepared in the manner of Example I except that the
precipitated silica, together with the silica coupling agent, were
added in the first non-productive mixing stage (NP1), as in Example
I, and the carbon black was added in the second non-productive
mixing stage (NP2), therefore subsequent to and entirely separate
from the silica to demonstrate an alternate method of preparation
of the respective rubber compositions.
[0075] The basic recipe for the rubber compounds is presented in
the following Table 3 and recited in parts by weight unless
otherwise indicated.
[0076] The recipe is similar to the recipe recited in Table 1 of
Example I except for the indicated addition of the carbon black in
the second non-productive mixing step (NP2).
TABLE-US-00003 TABLE 3 Parts Non-Productive Mixing Step (NP1),
(mixed to about 160.degree. C.) Cis 1,4-Polyisoprene natural
rubber.sup.1 50 Polybutadiene rubber.sup.2 50 Silica.sup.3 30
Silica coupling agent.sup.4 2.4 Rubber processing oil and resin 7
Wax and antioxidant 5.5 Stearic acid 1 Non-Productive Mixing Step
(NP2), (mixed to about 160.degree. C.) Carbon black N550 (N550 is
an ASTM designation) 30 Productive Mixing Step (PR), (mixed to
about 110.degree. C.) Sulfur 1.5 Zinc oxide 1.5 Antioxidant 1.25
Sulfenamide sulfur cure accelerator 2.1
[0077] The following Table 4 illustrates processing characteristics
and various physical properties of rubber compositions based upon
the basic recipe of Table 3.
TABLE-US-00004 TABLE 4 Rubber Compound Numbers 6 7 8 9 10
Elastomers (phr) Natural Rubber 50 50 50 50 50 Cis
1,4-polybutadiene A 50 0 0 0 0 Cis 1,4-polybutadiene B 0 50 0 0 0
Amine functionalized polybutadiene C 0 0 50 0 0 TEOS functionalized
polybutadiene D 0 0 0 50 0 Imine-TEOS functionalized 0 0 0 0 50
polybutadiene E Rheometer, 170.degree. C. Maximum torque (dNm) 16
16.6 17 17.9 18.6 Minimum torque (dNm) 3 3.2 2.9 3.9 4.7 T90
(minutes) 3.5 3.5 4.1 4 3.9 Mooney Scorch, 120.degree. C. Scorch
time 5 pt rise (minutes) 33.5 31.9 34.8 35.8 35.5 RPA Analyzer,
100.degree. C. Cured G' at 1% strain (MPa) 2.3 2.3 2.5 2.5 2 Cured
G' at 10% strain (MPa) 1.4 1.5 1.6 1.6 1.6 Tan delta at 10% strain
0.158 0.137 0.139 0.136 0.123 Stress-strain, ATS, 11 min,
170.degree. C. Tensile strength (MPa) 19.2 19.4 19.6 19.6 17.7
Elongation at break (%) 713 680 696 687 590 100% modulus (MPa) 1.4
1.4 1.5 1.6 1.6 300% modulus (MPa) 6.4 6.7 6.3 6.8 7.5 Rebound
23.degree. C. 51.4 54.3 55.1 56.7 58.8 100.degree. C. 61.2 63.3
63.3 65.5 67.8 Shore A Hardness 23.degree. C. 59 59 60 62 62
100.degree. C. 54 55 55 57 58 DIN Abrasion, 23.degree. C. Relative
Vol. Loss 77 68 81 78 73 RDS Strain Sweep, 10 Hertz, 30.degree. C.
Storage modulus (G') at 10% 1.5 1.5 1.7 1.7 1.8 strain, (MPa) Tan
delta, at 10% strain 0.157 0.140 0.136 0.128 0.116
[0078] It can be seen from Table 4 that, as in Example 1, that the
replacement of high cis 1,4 polybutadiene rubber A with cis
1,4-polybutadiene rubber B or functionalized polybutadiene rubber C
through E did not affect the rubber processing (Mooney scorch time)
and cure dynamics (MDR analysis) of the rubber composition.
[0079] This is considered to be significant in a sense, as will be
discussed hereafter, that the enhancement of physical properties
such as rebound and hysteresis loss indicative tan delta by the use
of functionalized polybutadienes C through E instead of the
non-functionalized polybutadiene elastomers A and B, in combination
with silica and a silane coupling agent, was not at the expense of
processibility, insofar as the Mooney scorch time as well as T90
cure time were concerned, of the rubber composition.
[0080] It can further be seen from Table 4 that the rebound values
at room and high temperatures of the rubber composition were
significantly improved through the use of functionalized
polybutadiene in combination with silica and a silane coupling
agent. The rebound value at 23.degree. C. and 100.degree. C. of the
rubber compound 10 containing the imine-TEOS functionalized
polybutadiene, for example, was about 7 points higher than that of
the comparative (Control) rubber compound 6.
[0081] Also, it can further be seen that the hysteresis loss
indicative tan delta at 30.degree. C. of the rubber composition was
significantly enhanced (reduced) as a result of replacing the
non-functionalized cis 1,4-polybutadiene elastomer A or B of rubber
Comparative (Control) rubber compounds 6 and 7 with the amine, TEOS
and imine-TEOS functionalized cis 1,4-polybutadiene elastomers C
through E for the rubber compounds 8, 9 and 10.
[0082] In particular, the tan delta values for rubber compounds 8,
9 and 10 were only 0.136, 0.128 and 0.116, respectively, which were
significantly lower that the value of 0.157 for comparative
(Control) rubber compound 6.
[0083] Similarly, the hysteresis loss tan delta value at the higher
temperature of 100.degree. C. of the rubber compound 10, for
example, was beneficially significantly lower than that of the
Comparative (Control) rubber compound 6.
[0084] Some improvement in rebound and hysteresis loss tan delta
was seen when non-functionalized polybutadiene B was used to
replace the non-functionalized polybutadiene A. However, the degree
of improvement was not as significant as that achieved through the
use of functionalized polybutadiene C, D or E. Overall, TEOS and
imine-TEOS functionalized polybutadienes D and E are seen as being
the most effective in enhancing the hysteresis loss properties of
the rubber composition as seen from rubber compounds 9 and 10.
[0085] This is considered to be significant in the sense that a
rubber composition with high rebound values and low hysteresis loss
tan delta values at room and high temperatures are predictive of
low internal heat build up during the working of the rubber
composition with an attendant low temperature rise and predictive
of reduced rolling resistance for a tire with a tire component such
as for example, outer sidewall rubber layer or subtread rubber
layer composed of such rubber composition with a predictive
improved fuel economy for an associated vehicle.
[0086] It can be noted that, in comparison with adding carbon
black, silica and the silica coupling agent together in the first
non-productive mixing stage (NP1) followed by a second
non-productive mixing stage (NP2) without further addition of
ingredients as presented in Example 1, adding silica and the silane
coupling agent in first non-productive mixing stage (NP1) followed
by addition of the carbon black in the second non-productive mixing
stage (NP2) for this Example II led to an observed less improvement
in the hysteresis loss properties of the rubber composition through
the use of functionalized polybutadiene for the rubber composition
which also contained the silica and silica coupling agent.
[0087] It can also further be seen from Table 4 that the abrasion
resistance of the rubber composition was in general improved or at
least maintained through the use of functionalized polybutadiene in
combination with silica and a silica coupling agent. This is
considered to be significant in a sense that the enhancement of
rubber composition hysteresis properties from the use of
functionalized polybutadiene in combination with silica and a
silane coupling agent, with the carbon black being added in the
second non-productive mixing stage, was not at a significant
expense of the abrasion resistance of the rubber composition.
[0088] This example demonstrates a significant benefit relating to
the addition sequence of carbon black, silica and silica coupling
agent in achieving the desirable hysteresis loss properties of the
rubber composition when functionalized polybutadiene is used to
replace the non-functionalized cis 1,4-polybutadiene rubber.
EXAMPLE III
[0089] Rubber compositions (compounds) composed of a combinations
of natural rubber (cis 1,4-polyisoprene rubber) and various
polybutadiene rubbers, including functionalized polybutadiene
elastomers, were prepared.
[0090] The rubber compounds 1 through 5 of Example I are similar to
rubber compounds 11 through 15, respectively, for this Example III
insofar as polybutadienes and functionalized polybutadienes used
are concerned.
[0091] For this Example III, the rubber compositions were prepared
in the manner of Example I except that the precipitated silica,
together with the silica coupling agent, were added in the second
non-productive mixing stage (NP2) and carbon black was added in the
first non-productive mixing stage (NP1) to demonstrate an alternate
method of preparation of the respective rubber compositions.
[0092] The basic recipe for the rubber samples is presented in the
following Table 5 and recited in parts by weight unless otherwise
indicated.
[0093] The recipe is similar to the recipe recited in Table 1 of
Example I except, as indicated above, that the addition of the
silica and silica coupling agent is made in the second
non-productive mixing step (NP2) instead of the first
non-productive mixing step (NP1) as was done in the previous
Example I.
[0094] The rubber compositions were prepared in the manner of
Example II in a sense of mixing the ingredients in three sequential
mixing steps, namely a non-productive mixing step (NP1) followed by
second non-productive mixing step (NP2) and then by a productive
mixing step (PR) in which sulfur curatives were added.
[0095] The basic recipe for the rubber compounds is presented in
the following Table 5 and recited in parts by weight unless
otherwise indicated.
TABLE-US-00005 TABLE 5 Parts Non-Productive Mixing Step (NP1),
(mixed to about 160.degree. C.) Cis 1,4-Polyisoprene natural
rubber.sup.1 50 Polybutadiene rubber.sup.2 50 Carbon black N550
(N550 is an ASTM designation) 30 Rubber processing oil and resin 7
Wax and antioxidant 5.5 Stearic acid 1 Non-Productive Mixing Step
(NP2), (mixed to about 160.degree. C.) Silica.sup.3 30 Silica
coupling agent.sup.4 2.4 Productive Mixing Step (PR), (mixed to
about 110.degree. C.) Sulfur 1.5 Zinc oxide 1.5 Antioxidant 1.25
Sulfenamide sulfur cure accelerator 2.1
[0096] The following Table 6 illustrates processing characteristics
and various physical properties of rubber compositions based upon
the basic recipe of Table 5.
TABLE-US-00006 TABLE 6 Rubber Compound Numbers 11 12 13 14 15
Elastomers (phr) Natural Rubber 50 50 50 50 50 Cis
1,4-polybutadiene A 50 0 0 0 0 Cis 1,4-polybutadiene B 0 50 0 0 0
Amine Functionalized polybutadiene C 0 0 50 0 0 TEOS functionalized
polybutadiene D 0 0 0 50 0 Imine-TEOS functionalized 0 0 0 0 50
polybutadiene E Rheometer, 170.degree. C. Maximum torque (dNm) 16.6
17.6 18.2 19.8 18.6 Minimum torque (dNm) 3.1 3.2 3.1 4.3 4.9 T90
(minutes) 3.8 3.6 4.2 4 3.9 Mooney Scorch, 120.degree. C. Scorch
time 5 pt rise (minutes) 38.8 33.9 38.1 34.1 37.2 RPA Analyzer,
100.degree. C. Cured G' at 1% strain (MPa) 2.4 2.5 2.7 2.8 2.4
Cured G' at 10% strain (MPa) 1.7 1.8 2.0 2 1.9 tan delta at 10%
strain 0.157 0.147 0.152 0.136 0.121 Stress-strain, ATS, 11 min,
170.degree. C. Tensile strength (MPa) 18.3 20.4 19.7 19.8 19.4
Elongation at break (%) 708 725 716 680 667 100% modulus (MPa) 1.3
1.4 1.5 1.7 1.5 300% modulus (MPa) 5.9 6.3 6.1 6.9 6.9 Rebound
23.degree. C. 49.9 52.6 53.6 55.6 57.6 100.degree. C. 59.4 61.3
61.9 64.7 65.4 Shore A Hardness 23.degree. C. 60 60 62 63 61
100.degree. C. 54 55 56 58 57 DIN Abrasion, 23.degree. C. Relative
Vol. Loss 78 73 87 81 78 RDS Strain Sweep, 10 Hertz, 30.degree. C.
Storage modulus (G') at 10% 1.5 1.5 1.8 1.8 1.7 strain, (MPa) Tan
delta at 10% strain 0.167 0.148 0.142 0.132 0.126
[0097] It can be seen from Table 6 that, as in Example 1 and
Example II, the replacement of high cis 1,4 polybutadiene rubber A
with cis 1,4-polybutadiene rubber B or functionalized polybutadiene
rubber C through E did not affect the rubber composition processing
(Mooney scorch time) and cure dynamics (MDR analysis) of the rubber
composition.
[0098] This is considered to be significant in a sense, as will be
discussed hereafter, that the enhancement of the indicated physical
properties of the rubber composition by the use of functionalized
polybutadiene in combination with silica and a silane coupling
agent was not at a significant the expense of processibility of the
rubber composition.
[0099] It can further be seen from Table 6 that the rebound values
at room and high temperatures of the rubber composition were
beneficially significantly improved through the use of
functionalized polybutadiene in combination with silica and a
silane coupling agent. The rebound value at 23.degree. C. and
100.degree. C. of the rubber compound 15 using the imine-TEOS
functionalized polybutadiene E, for example, was about 6 to 7
points higher than that of the comparative (Control) rubber
compound 11 using the non-functionalized polybutadiene A.
[0100] Also, it can further be seen that the hysteresis loss
indicative tan delta at 30.degree. C. of the rubber composition was
significantly enhanced (reduced) as a result of replacing the
non-functionalized cis 1,4-polybutadiene elastomer A or B of rubber
compounds 11 and 12 with the amine, TEOS and imine-TEOS
functionalized cis 1,4-polybutadiene elastomers C through E for the
rubber compounds 13, 14 and 15.
[0101] In particular, the tan delta values for rubber compounds 13,
14 and 15 were only 0.142, 0.132 and 0.126, respectively were
significantly lower that the value of 0.167 for comparative
(Control) rubber compound 11.
[0102] Similarly, the hysteresis loss tan delta value at the higher
temperature of 100.degree. C. of the rubber compound 15, for
example, was beneficially significantly lower than that of the
comparative (Control) rubber compound 11.
[0103] Some improvement is observed in rebound property and loss
tan delta predictive hysteresis loss property when
non-functionalized polybutadiene rubber B in Control rubber Sample
12 the non-functionalized polybutadiene rubber A in comparative
(Control) rubber compound 11.
[0104] However, the degree of improvement was not as significant as
that achieved through the use of functionalized polybutadiene
rubber. Overall, TEOS functionalized polybutadiene rubber D and
imine-TEOS functionalized polybutadiene E are seen as being the
most effective in enhancing the hysteresis loss properties of the
rubber composition. This is considered to be significant in the
sense that a rubber composition with high rebound values and low
hysteresis loss tan delta values at room and high temperatures
would predictively low internal heat build up during working
conditions for the rubber, with an attendant lower rate of internal
temperature and a predictive reduced rolling resistance for a tire
with a component such as, for example, outer sidewall rubber layer
or subtread rubber layer composed of such rubber composition with
an attendant improved fuel economy for an associated vehicle.
[0105] It can be noted that, in comparison with adding silica and
the silane coupling agent in the first non-productive mixing stage
(NP1) and carbon black in the second non-productive mixing stage
(NP2) as shown in Example II, adding carbon black in first
non-productive mixing stage (NP1) and silica and the silane
coupling agent in the second non-productive mixing stage (NP2) for
this Example III is seen to lead to even less improvement in the
hysteresis loss properties of the rubber composition through the
use of functionalized polybutadiene in combination with silica and
a silane coupling agent.
[0106] It can also further be seen from Table 6 that the abrasion
resistance of the rubber composition was in general maintained
through the use of functionalized polybutadiene in combination with
silica and a silane coupling agent. This is considered to be
significant in a sense that the aforesaid enhancement of hysteresis
properties of the rubber composition from the use of functionalized
polybutadiene in combination with silica and a silane coupling
agent was not at a significant expense of the abrasion resistance
of the rubber composition.
[0107] This example demonstrates the desirability and benefit of
using functionalized polybutadiene in combination with silica and a
silane coupling agent for enhanced hysteresis loss properties for
the rubber composition, hence predictive rolling resistance
performance without significant compromising of other indicated
physical properties of the rubber composition. This example also
illustrates the importance of the addition sequence of carbon
black, silica and silane coupling agents in achieving the desirable
hysteresis loss properties of the rubber composition when
functionalized polybutadiene is used to replace non-functionalized
cis 1,4 polybutadiene such as the non-functionalized polybutadiene
(A).
[0108] The following Table 7 is presented to focus upon a summary
of a significant procedural aspect of Examples I, II and III in a
sense of showing relative improvements in rebound and Tan delta
property values resulting from variations in order of addition of
rubber reinforcing carbon black and precipitated silica to the
rubber composition.
TABLE-US-00007 TABLE 7 Rubber Compounds Polybutadiene (PBd)/Natural
Rubber Blend From From From Compositions Example I Example II
Example III Rebound, at 100.degree. C. decrease in rebound is
indicative of reduction in hysteresis loss property Rebound Value
per (Rubber Compound No.) With cis 1,4-polybutadiene A 58.5 (1)
61.2 (6) 59.4 (11) With cis 1,4-polybutadiene B 62.3 (2) 63.3 (7)
61.3 (12) With Amine Functionalized polybutadiene C 65.2 (3) 63.3
(8) 61.9 (13) With TEOS Functionalized polybutadiene D 66.4 (4)
65.5 (9) 64.7 (14) With Imine-TEOS Functionalized 68.3 (5) 67.8
(10) 65.4 (15) polybutadiene E Strain Sweep analysis by RDS
analytical apparatus, at 10 Hertz, 30.degree. C. Tan delta value
taken at 10 percent strain - an increase in Tan delta value is
indicative of reduction in hysteresis loss property Tan delta Value
per (Rubber Compound No.) With cis 1,4-polybutadiene A 0.162 (1)
0.157 (6) 0.167 (11) With cis 1,4-polybutadiene B 0.139 (2) 0.140
(7) 0.148 (12) With Amine Functionalized polybutadiene C 0.126 (3)
0.136 (8) 0.142 (13) With TEOS Functionalized polybutadiene D 0.118
(4) 0.128 (9) 0.132 (14) With Imine-TEOS Functionalized 0.118 (5)
0.116 (10) 0.126 (15) polybutadiene E Summary of Mixing Sequences
for Carbon Black and Silica For Examples I, II and III For Example
I Carbon black, silica and coupling agent are all added in first
non- productive mixing stage For Example II Silica and coupler are
added in first non-productive mixing stage and carbon black is
added separately in a subsequent second non-productive mixing stage
For Example III Carbon black are added in first non-productive
mixing stage and Silica with coupler are added separately in a
subsequent second non-productive mixing stage
[0109] It can be seen from the summary presented in Table 7
that:
[0110] (A) that the best improvement in the hysteresis loss
property (namely an increase in the rebound and decrease in Tan
delta properties) was observed in Example I for rubber compounds 3,
4 and 5 containing the functionalized polybutadienes for which
carbon black, silica and coupling agent were added together with
the functionalized polybutadiene in the first non-productive mixing
stage (NP1).
[0111] (B) a lesser and more moderate improvement in the hysteresis
loss property (moderate increase in rebound and moderate decrease
in Tan delta properties) was observed in Example II for rubber
compounds 8, 9 and 10 containing the functionalized polybutadienes
when precipitated silica, together with coupling agent were added
with the functionalized polybutadiene in a first non-productive
mixing step, or stage (NP1), and the carbon black added in a second
non-productive mixing step, or stage (NP2) to the rubber
composition from said first non-productive mixing stage. Therefore,
the carbon black was added subsequent to and separately from the
precipitated silica addition.
[0112] (C) the least improvement in the hysteresis loss property
(moderate increase in rebound and moderate decrease in Tan delta
properties) was observed in Example III for rubber compounds 13, 14
and 15 containing the functionalized polybutadienes when carbon
black was added with the functionalized polybutadiene in a first
non-productive mixing step (NP1) and precipitated silica, together
with coupling agent, were added in a second non-productive mixing
step (NP2) to the rubber composition from the first non-productive
mixing stage. Therefore, the silica was added subsequent to and
separate from the carbon black addition.
[0113] Therefore, in further accordance with this invention, the
tire is provided where the rubber composition for at least one of
said outer sidewall rubber layer and said subtread rubber layer is
prepared by:
[0114] (A) mixing rubber reinforcing carbon black, precipitated
silica and silica coupling agent together with said functionalized
cis 1,4-polybutadiene elastomer in a preparatory non-productive
mixing step (NP), followed by a productive mixing step (PR) in
which sulfur curatives are added, or
[0115] (B) mixing precipitated silica, together with coupling
agent, are together with said functionalized cis 1,4-polybutadiene
elastomer in a first preparatory non-productive mixing step (NP)
followed by mixing rubber reinforcing carbon black in a subsequent
sequential second non-productive mixing step (NP) to the rubber
composition from said first non-productive mixing step, followed by
a productive mixing step (PR) in which sulfur curatives are added,
or
[0116] (C) mixing carbon black mixed with the functionalized cis
1,4-polybutadiene elastomer in a preparatory first non-productive
mixing stage (NP) followed by mixing precipitated silica and
coupling agent in a subsequent sequential non-productive mixing
step (NP) to the rubber composition from said first non-productive
mixing step, followed by a productive mixing step (PR) in which
sulfur curatives are added;
[0117] wherein said mixing steps are preferably conducted in an
internal rubber mixer to a temperature in a range of from about
140.degree. C. to about 170.degree. C. for said non-productive
steps and a temperature in a range of from about 100.degree. C. to
about 120.degree. C. for said productive mixing steps, and
[0118] wherein said rubber compositions are cooled to a temperature
below 40.degree. C. between said mixing steps.
[0119] While certain representative embodiments and details have
been shown for the purpose of illustrating the invention, it will
be apparent to those skilled in this art that various changes and
modifications may be made therein without departing from the spirit
or scope of the invention.
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